[Haskell-cafe] Associated data types

Andres Loeh andres at cs.uu.nl
Wed Dec 10 09:17:17 EST 2008


> Date: Wed, 10 Dec 2008 13:36:11 +0000
> From: Lennart Augustsson <lennart at augustsson.net>
> Subject: Re: [Haskell-cafe] Associated data types
> For an associated data type D, we know that the type function D is
> injective, i.e., for different indicies given to D we'll get different
> data types.  This makes much more powerful reasoning possible in the
> type checker.  If associated data types are removed there has to be
> some new mechanism to declare an associated type as injective, or the
> type system will lose power.
>   -- Lennart
> 2008/12/10 Eyal Lotem <eyal.lotem at gmail.com>:
> > If we have associated type synonyms, is there still reason to have
> > associated data types?


Another, somewhat related, issue is that associated type synonyms cannot
currently be partially applied, whereas associated data types can.



Andres Loeh, Universiteit Utrecht

mailto:andres at cs.uu.nl     mailto:mail at andres-loeh.de

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